Vacuum processing systems for processing 100 mm, 200 mm, 300 mm or other diameter wafers are generally known. An example of a typical vacuum processing system 10 is shown in FIG. 1a. The system 10 typically has a centralized transfer chamber 12 mounted on a monolith platform (not shown). The transfer chamber 12 is the center of activity for the movement of wafers being processed in the system. One or more process chambers 14 attach to the transfer chamber 12 at valves through which the wafers are passed by a robot 16 in the transfer chamber 12. The valves are selectively opened and closed to isolate the process chambers 14 from the transfer chamber 12 while wafers are being processed in the process chamber 14. Physically, the process chambers 14 are either supported by the transfer chamber 12 and its platform or are supported on their own platform. Inside the system 10, the transfer chamber 12 is typically held at a constant vacuum; whereas, the process chambers 14 may be pumped to a greater vacuum for performing their respective processes. Afterward, the chamber pressure must be returned to the level in the transfer chamber 12 before opening the valve to permit access between the chambers.
The transfer chamber 12 has facets to support four process chambers 14 and two load lock chambers 18. Other transfer chambers may have a total of only four or five facets. The process chambers 14 include rapid thermal processing (RTP) chambers, physical vapor deposition (PVD) chambers, chemical vapor deposition (CVD) chambers, etch chambers, etc. The productivity of a vacuum processing system 10 is increased when more process chambers 14 are mounted to the transfer chamber 12, because more wafers can be processed at a given time. Additionally, less space is required in the manufacturing facility if the productivity of the system is maximized.
Access to the transfer chamber 12 for wafers from the exterior of the system 10, or from the manufacturing facility, is typically through one or more load lock chambers 18. The load lock chambers 18 cycle between the pressure level of the ambient environment and the pressure level in the transfer chamber 12 in order for the wafers to be passed therebetween. The load lock chambers 18 attach to an optional mini-environment 20 which transfers wafers in a very clean environment at atmospheric pressure from wafer pods seated on pod loaders 22 to the load lock chambers 18. Typically, the transfer chamber 12 or the mini-environment 20 has a wafer orienter, or aligner 24 for aligning a wafer so that the wafer is properly oriented when it is loaded into a process chamber 14 or a load lock chamber 18. For systems 10 that do not have a mini-environment 20, the wafer aligner 24 is attached to the transfer chamber 12 at one of the locations for a process chamber 14. For systems 10 that have a mini-environment 20, the wafer aligner 24 is located in a small side chamber 26 attached to the mini-environment 20 between the pod loaders 22 as shown in FIG. 1a or at one end 60, 62 of the track system for the track-mounted robot 28. One or more track-mounted mini-environment robots 28, 29 transfer the wafers from the pod loaders 22 to the load lock chambers 18.
In a typical loading procedure in a mini-environment 20 having a wafer aligner side chamber 26, a robot 28 moves a wafer out of a pod positioned on a pod loader 22 in the direction of arrow A. The robot 28 moves to the wafer aligner 24 in the direction of arrow B. The robot 28 inserts the wafer into the wafer aligner 24 in the direction of arrow C. After the wafer aligner 24 aligns the wafer, the robot 28 retrieves the wafer in the direction of arrow D. The robot 28 moves in the direction of arrow E toward the load lock chamber 18 to position the wafer for delivery therein. Finally, the robot 28 inserts the wafer into the load lock chamber 18 in the direction of arrow F. Thus, six movements of the wafer are required to move the wafer from a pod to a load lock chamber 18. If the number of movements can be reduced, then the time to load the load lock chamber 18 can be reduced and the throughput of the system 10 increased.
A system 10 typically has only one robot 28, but if the system 10 has two robots 28, 29, as shown in FIG. 1a, then the two robots 28, 29 must share the wafer aligner 24 and the space directly in front of the wafer aligner 24 in the mini-environment. If the first robot 28 moves into this space to deliver a wafer to the wafer aligner 24 or a load lock chamber 18, then the first robot 28 may interfere with the second robot's performance. The first robot 28 must move out of the way before the second robot 29 can move into this space. Thus, if the movements of the robots 28, 29 are not carefully coordinated, then the second robot 29 may become idle while waiting for the first robot 28 to finish accessing the wafer aligner 24 or the load lock chamber 18. Time spent waiting by one robot 29 for the other robot 28 to move causes an increase in the time to load the wafers and a decrease in the throughput of the system 10.
Another example of a typical vacuum processing system 30 is shown in FIG. 1b. This example has a transfer chamber 32 mounted on a monolith platform (not shown) and four process chambers 34 mounted to the transfer chamber 32 similar to the example in FIG. 1a, but the system 30 also has a buffer chamber 36 for staging the movement of wafers through the system 30 and for providing pre-processing and post-processing of the wafers as needed. Disposed between the transfer chamber 32 and the buffer chamber 36 are a pre-clean chamber 38 and a cool-down chamber 40. The buffer chamber robot 42 places wafers to be processed into the pre-clean chamber 38, and the transfer chamber robot 44 removes the wafers from the pre-clean chamber 38 and transfers the wafers to one or more process chambers 34 for processing. The pre-clean chamber 38 provides cleaning of the wafers and transitioning from the buffer chamber pressure to the transfer chamber pressure. After processing, the transfer chamber robot 44 places the wafers in the cool-down chamber 40, and the buffer chamber robot 42 removes the wafers from the cool-down chamber 40. The cool-down chamber 40 provides for post-process cooling of the wafers and for pressure transitioning from the transfer chamber pressure to the buffer chamber pressure. The buffer chamber robot 42 transfers the wafers to the load lock chambers 46 for return to the ambient environment or transfers the wafers to an expansion chamber 48 for additional processing or post-processing or to a cool-down chamber 50 for further cooling before transferring the wafers to the load lock chambers 46. The load lock chambers 46 transition the wafers between the buffer chamber pressure and the ambient environment pressure.
As in the system 10 shown in FIG. 1a, the load lock chambers 46 have an optional mini-environment 54 attached thereto. The mini-environment 54 has pod loaders 56 attached thereto and one or more mini-environment robots 58 disposed therein for moving the wafers between the load lock chambers 46 and wafer pods seated on the pod loaders 56. The mini-environment 54, however, does not have a wafer aligner in a side chamber, because such systems 30 have typically attached a wafer aligner chamber 52 to the buffer chamber 36 for aligning the wafers and permitting the wafers to degas after they pass through the load lock chambers 46. However, it is possible to place a side chamber on the mini-environment 54 for housing a wafer aligner at a location 64 between the pod loaders 56 or at one of the ends 66, 68 of the track system for the track-mounted robot 224, as shown in FIG. 1a. The buffer chamber robot 42 moves the wafers from the load lock chambers 46 to a wafer aligner in the wafer aligner chamber 52 and then to the pre-clean chamber 38, or to an expansion chamber 48 for pre-processing if necessary before transferring the wafers to the pre-clean chamber 38. In this system 30, the wafer movement in the mini-environment 54 requires only three basic steps to move the wafers from the pod loaders 56 to the load lock chambers 46, but the wafer movement in the buffer chamber 36 requires extra steps to move the wafers into and out of the wafer aligner chamber 52. These extra steps in the movement of wafers in the buffer chamber 36 increase the time required to transfer wafers therethrough and decrease the throughput of the system 30. Additionally, since the wafer aligner chamber 52 occupies one of the facets on the buffer chamber 36 that could be used by another chamber for performing a pre-processing or post-processing step on the wafers, the throughput of the system 30 may be further reduced.
A need, therefore, exists for a mini-environment with a placement and configuration of a wafer aligner that provides for a minimum number of wafer movements and a minimum amount of robot interference in order to maximize system throughput.